CHE 350 Lecture Notes - Lecture 1: Osmosis, Polymerization, Acid Dissociation Constant

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Chapter 1 – Intro to the Chemistry of Life
Energy is conserved  neither created nor destroyed
System = what’s of interest  has X amount of energy (U)
Surroundings = rest of it
Heat = q Work = W Enthalpy = H Entropy = S
Entropy tends to Increase
oSpontaneous processes are characterized by the conversion of order to disorder
oDisorder = the # of ways to arrange parts of a system, all of which are
energetically equiv
oThere are more ways to arrange a disordered (random) system than an ordered
system
More ways = bigger chance of it happening
oGibbs free energy = Available energy (G)
oG = 0  REVERSIBLE | FORWARD AND REVERSE RXNS ARE BALANCED =
EQUILIBRIUM
oG < 0  IRREVERSIBLE (FAVORABLE) | EXERGONIC, SPONTANEOUS
oG > 0  IRREVERSIBLE (UNFAVORABLE) | ENDERGONIC, NOT SPONTANEOUS
Le Chatelier’s Principle: any deviation from equilibrium starts a process to restore the
system to equilibrium
Standard State Conventions: t =25, p = 1 atm
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oStandard free energy (or changes in it) are valid only at pH of 7 in biochemical
rxns
Thermo usually applies to reversible processes in isolated systems (can’t exchange
anything with the surroundings) or closed systems (energy transfer only). Isolated
systems tend to reach equilibrium.
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Chapter 2 – WATER = H2O
Nearly all bio molecules assume their shapes (functions) in response to surrounding
water
A medium for majority of biochem rxns = H2O
H2O participates in chem rxns (-OH + H+)
1) Water is polar
a. Forms H-bonds
2) Hydrophilic substances dissolve in H2O
a. Polar ionic things H2O
b. Nonpolar – hydrophobic
c. Like dissolves like
3) Hydrophobic effect
a. Causes nonpolar substances to aggregate in H2O  protein, nucleic acids, cellular
membranes all get their shape this way
b. H-bonds of H2O are disturbed and since nonpolar molecs can’t accept/donate H-
bonds, H2O can’t do what it usually does (H-bond to molecs)
c. So H2O forms H-bonds enclosing the cavity (entropy ), same # of H-bonds
formed by some rotational + translational freedom is lost
d. Net result = unfavorable G of hydration of nonpolar substance caused by
ordering of surrounding H2O molecs
e. Substance is then excluded from the aqueous phase
f. Aggregation = minimizes surface area of cavity the substance takes up =
maximizes entropy of the whole system = more H2O molecs can interact with
each other
Amphiphillic = hydrophobic and hydrophilic segments
f.i. Ex: fatty acids
Osmosis = net movement of solvent across the membrane from a region of high
concentration (ex: pure H2O) to love concentration (H2O w/ dissolved solute)
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Document Summary

Chapter 1 intro to the chemistry of life. Energy is conserved neither created nor destroyed. System = what"s of interest has x amount of energy (u) More ways = bigger chance of it happening: gibbs free energy = available energy ( g, g = 0 reversible | forward and reverse rxns are balanced = Equilibrium: g < 0 irreversible (favorable) | exergonic, spontaneous, g > 0 irreversible (unfavorable) | endergonic, not spontaneous. Le chatelier"s principle: any deviation from equilibrium starts a process to restore the system to equilibrium. Standard state conventions: t =25 , p = 1 atm: standard free energy (or changes in it) are valid only at ph of 7 in biochemical rxns. Thermo usually applies to reversible processes in isolated systems (can"t exchange anything with the surroundings) or closed systems (energy transfer only). Nearly all bio molecules assume their shapes (functions) in response to surrounding. A medium for majority of biochem rxns = h2o.

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